Perform mutate in columns simultaneously

Question

Hello,

I have a dataframe where I want to apply the same function in several columns at the same time. I tried to use the dplyr::mutate_at but I don’t think I understand the logic of this operation.

First what I can do:

df <- data.frame(col1 = c(1:3), col2= c(4:6), col3 = c(7:9))

percentualize <- function(x){

    x <- paste0(x, "%")


}

library(tidyverse)

df %>%
  mutate(col1 = percentualize(col1),
         col2 = percentualize(col2),
         col3 = percentualize(col3))

How could I operate in these three columns at once without having to keep repeating?

Answer 1

You can do it like this:

library(tidyverse)

df %>% 
  mutate_at(.vars = vars(contains('col')), .funs = funs(. = percentualize))

  col1 col2 col3 col1_. col2_. col3_.
1    1    4    7     1%     4%     7%
2    2    5    8     2%     5%     8%
3    3    6    9     3%     6%     9%

Editing

If variables have something in common, you could use this feature to call them all at once. Consider the new names below:

df %>%
  mutate(coluna = percentualize(col1),
         variavel = percentualize(col2),
         lambda = percentualize(col3))

As all variables have the letter l in common, you can do this:

df %>% 
  mutate_at(.vars = vars(contains('l')), .funs = list(. = percentualize))

That would give the same result:

  col1 col2 col3 col1_. col2_. col3_.
1    1    4    7     1%     4%     7%
2    2    5    8     2%     5%     8%
3    3    6    9     3%     6%     9%

Variables may not have common names, often. But their classes may have similarity. So you can do an analysis by the object class, not by its names. Suppose its variables are class numeric. With mutate_if you do that:

df %>% 
  mutate_if(is.numeric, .funs = funs(. = percentualize))

  col1 col2 col3 col1_. col2_. col3_.
1    1    4    7     1%     4%     7%
2    2    5    8     2%     5%     8%
3    3    6    9     3%     6%     9%

Anything of a class numeric will be considered in the analysis.